Third Generation Partnership Project (3GPP) standards for mobile communication define applications for various interfaces in the Internet Protocol (IP) Multimedia Subsystem (IMS) network. In the IMS reference architecture, the home subscriber server (HSS) comprises a subscriber database which holds all information about subscribers and their subscriptions. Access to any information regarding this profile needs to be queried from the HSS such as the location, authorization for conferencing, etc. Required messages are defined in terms of a command set identified by various reference points, such as Cx/Dx, Sh, Rf/Ro, Gq, Wx, Bi. Hence, on subscriber related interfaces, such as Cx and Sh, requests to access and update a subscriber profile are transferred. A base protocol defines the basic Diameter message format. Data is carried within a Diameter message as a collection of Attribute Value Pairs (AVP). An AVP consists of multiple fields: an AVP Code, a Length, Flags, and Data. Some AVPs are used by the Diameter base protocol itself—other AVPs are intended for Diameter applications.
Access to the IMS network or other types of core networks is possible by using a wide range of access technologies. Mobile access via the General Packet Radio Services (GPRS) or Universal Mobile Telecommunications System (UMTS) plays an important role as such an access technology. Knowledge about the position, location, or access technology and monitoring of movement profiles of mobile subscribers is important for network operators of the IMS or other core networks to provide for example charging services, lawful interception, and other services depending on the position or location of the subscriber, or the type of access network.
More specifically, knowledge about the position of a subscriber and his or her positional change (i.e., roaming) allows charging of a use of IMS services independent from the actual position or location of the subscriber or user, as is usual in fixed networks. In big countries this information is interesting for network operators, to differentiate charging of local calls and far-distance calls. For lawful interception usefulness of this information is also apparent. The same applies to location dependent services, such as traffic congestion information, advertisement or transmission of location information to friends and family, as e.g. kid tracking services.
However, a problem resides in that, so far, direct transmission of position-related or network-related information and its change from the access network to those nodes in the IMS or core network which are responsible for charging, interception and other related services was not standardized or automated.